MEPS 131:17-34 (1996) - doi:10.3354/meps131017

Factors affecting spatial variability in seine net catches of fish in the surf zone of False Bay, South Africa

Clark BM, Bennett BA, Lamberth SJ

Ichthyofaunal assemblages at 11 surf zone localities along the perimeter of False Bay, South Africa, were sampled by seine netting at monthly intervals between July 1991 and June 1993. Sampling localities were selected to encompass as wide a range of
physical variables as possible, incorporating sheltered, exposed, sandy and mixed-shore habitats, thus providing a comprehensive assessment of the factors influencing surf zone fish assemblages. Data collected at each site were averaged over the 2 yr
period in order to highlight the influence of various physical environmental variables on the abundance and community structure of these assemblages. Atherina breviceps, Liza richardsonii and Rhabdosargus globiceps were numerically
dominant at all sites, together providing between 69 and 99% of the catches. Overall, catches of juvenile fish exceeded that of adult fish, making up almost 53% of the catch. Fish abundance (no. ind. per 100 m2) and number of species recorded
at each site ranged from 6 to 199 and from 12 to 31 respectively. Multivariate analyses indicated that the degree of wave exposure, the presence of emergent rock on the shore and turbidity were responsible for most of the spatial variability in abundance
and community structure observed. Although of lesser importance, abundance of detached macrophytes, salinity and water temperature also played a role in structuring fish assemblages. Species specific preferences for varying combinations of these variables
are responsible for fluctuations in the structure and overall abundance of assemblages in different areas.